Re: Cat 977H Recoil Spring Bolt

Just a heads up before you think about buying a used recoil spring from a parted out machine. To be installed per the factory, the spring sets in it's spot in the roller frame housing, and is under tension against the frame, not the bolt. In other words the through bolt you are looking for has only one purpose, to hold the spring under tentson, in a short enough condition to install it into and remove it from the machine. Basically the spring assembly is put together a bit short, and when the assembly is in it's spot the nut on the end of the through bolt is backed off until the bolt is no longer under any tension at all, and all of the spring force is being held by the track frame. Talk to your machine shop about this and they may be more inclined to help when they know the througbolt is basically nothing more than an instillation/removal tool.

I say that to say this. The majority of the time the through bolts on the recoil springs get so corroded that you can't use them to collapse the spring enough to get it out of it's spot. When this happens the only way to remove a spring is to cut it, multiple times, in order to relieve the tension on it.(I cut the ones on the 977 I did about 6 more times...and they were each already broken in 5or 6 places already) That being the case when one is removed from a parts machine, 99.99999999999% of the time it's going to have to be junked/cut to get even get it out, otherwise they may have jerked it out somehow and it most likely will be too long to go back into it's mount on the new machine without being compressed and held there....by the screwed up through bolt that wasn't usable when it was removed from the donor. Didn't think to mention this in my last post, but after seeing a few relies about getting one from a junk machine I thought I ought to bring it up so you'd know. Good luck.

Wayne, your advice is right on 99.9 per cent of the time, but I have to disagree with you this time. The center bolt in the recoil spring is used to hold the spring to a certain length, specified by Cat. Don't back it off after you install it in the track frame. The spring isn't used to put tension on the track, the track adjuster is. It will compress if you get something stuck between the track and the sprocket, for instance, but normally it just sits there.I do agree with your advice about getting a new spring, though. If its available and within the budget.

The recoil spring doesn't provide tension, that's right. What it does is sets in the track frame with the rear end against a support that keeps if from moving rearward, and has a hole in the middle that the end of the through bolt goes through to keep it from jumping up and out/away from the support. (((I fabricated and welded up the whole setup on both sides of the one I redid as they were both rusted away to the point of being bent and unsafe))) On the front, the assembly sets on two ears that are captured between the frame and two bolt down plates that allow the spring to compress and move rearward should something get into the track.

That being the case there is a given distance between the rear support and the place the two ears set that has to be right or you can't put the assembly in and still bolt the hold down plates back on.

That being said, what dependzic says is exactly what I remember the manual saying. I wish I had it close but the manual I used on the 977 belonged to the customer. Further, the way I remember it, what you say is true, there is a specified length to the assembly. The way it works though is that the length is given to insure the assembly will fit back into the spot where it sets without being too long or short, nothing more. If it's off either way then the hold down plate will not bolt on and you have a BIG problem. From there there is another spec to back the nut off and then use the center bolt to lock it in lock it in place. Believe me, if one is put toether too short or too long it is BIG and a royal PITA. The two assemblies I had to install were both, thankfully, or unfortunately, given the point of view, way too short, and not too long. If they were too long I don't know what we would have done because there would have been no good way to hold it to tighten the nut. That would have been a BIG problem because to back off the nut it being under so many tons of force, took me and another guy, using a 24 inch adjustable wrench with about a 8 foot pipe handle, nearly an hour per side to back off the nuts and get everything right.

According to my service manual, step 5 in installation says that after the assembly is locked down into the stops: "back off the tension adjuster nut until the spring tension is against the stops, and continue turning until the nut extends 1/16" beyend the end of the bolt, then lock it in place at the end of the spring bolt with the locking bolt and washer".

That would indicate that the spring bolt and nut are there only to facilitate installation of the assembly.

NCWAYNE_-when I installed my 941b recoil spring it was separate from the center bolt. My friend had a 50 ton press and he had to build a jig to hold the spring sideways from shooting out and compressed it to the specified length so it could be installed.i doubled nut the bolt so the 14 ton load didn't let go!! but I had no trouble backing the nuts off

I can't remember exactly, but if I'm thinking right, the compression force on the 977 springs is well over 20 tons. That being said, the set length on th springs typically puts the ears right at the front of the hold down brackets so the nut doesn't have to be backed off but a little bit to release the spring to where it's resting in place. The ones I was dealing with had been compressed over an inch too far. As such there was a full inch that we had to back out the nut something like 1/8 turn at a time. The one on the left side where we were pulling down wasn't easy, but the one on the right side where we were having to pick up was a real pain.

Thanks Wayne, I had these thoughts when I first started looking, which was why I went ahead and bought new parts. I was hoping to find an assemble where the bolt and nut were in good enough shape to re-use with new spring parts. Looking like a no go.

Had no idea a new bolt and nut would be so hard to come by.

BTW I hear ya about cutting the spring. Mine was broke in about four places, and still had a bunch of tension in it. Ended up cutting a bunch more loops, and kept cutting until whacking with a big hammer showed all the tension out of it.

I know what your saying, but out of all of the ones I have ever seen, be it in a dozer, loader, excavator, etc, ((and brand seems to make no difference)) simply collapsing the spring to remove it from the track frame really isn't the problem. Like you say, it can be collapsed without using the nut, but the problem is that with the through bolt, 99.99999% of them are corroded to the point that the threads were gone, beat up until the threads weren't repairable, or any other kind of 'damaged' you can think of.

That's why I said what I did about buying a used one. If the threads are messed up, it doesn't matter if you can compress it and remove it with no problem, the problem is that there is no way to safely recompress it, and hold it in that state long enough to install it into the frame.

Not to mention your still putting a spring that has seen a hard life back into a spot where abuse is going to continue to occure. Given the cost to buy used and get it shipped, and the cost to buy a new one, all rolled in with ll of the work necessary to break a track, cut a broken spring out, etc, etc, etc, to me it's just not worth taking the chance on a used one unless there is nothing else available at all.

That's the advice I'd give any of my customers and I'll stick by it in 99.999% of the circumstances I can think of.

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